f150 acts like a dead battery when warm

Have you tested the battery? It may not be holding a charge

If the charging system is working properly and the battery is not run down, I'd have the starter checked even though it is new, assuming it is a rebuilt starter. Also make sure all your connections are clean and tight.

yes everything is new(rebuilt) new cable's had the starter bench tested ,,,it only happen's after it warms up...it can sit for days and will start right up...drive to the store 7 miles and acts like a dead battery wait 1/2 hour starts right up..

What about timing? Check the timing.

yes going to get up in the morning and R&R all my connections I has to be a bad connection....

So... it sounds like the battery is not getting charged by the Alternator... the car runs for a time (until the battery is drained) and then it sits (it may appear to be dead but can still hold and produce a charge) will start the car. Or the Alternator is not putting out enough to run the car and is trickling a charge to the battery which is not getting charged enough to keep up with the autos power consumption. Check the voltage in the morning, then run the car (until it dies) then check the voltage again. It will signal an issue in the charging system. Also check the Voltage of the Alternator out.

New alternator doesn't mean that it is working, like A.K. there is mentioning, but I assume no light on the dash or the gage is reading normal? If you have a volt meter check at the battery when running to make sure you have 14.5 to 14.7V. Let us know on the timing..

that's all been checked..i'm leaning towards a loose connection, loose ground